Conventionally, a substrate conveying robot comprising an end effector having a plurality of blades each of which holds a wafer (substrate) and a function of converting their pitch in the vertical direction is known. By this type of end effector, a plurality of wafers stored in a cassette or the like can be held at the same time so as to be conveyed.
Note that, as illustrated in FIG. 20, a plurality of wafers W in a cassette C are sometimes placed in the cassette C varying in the front-rear direction. Namely, not all the wafers W is positioned in a deepest position D, some wafers W are displaced forward from the wafer deepest position D.
Therefore, when a plurality of wafers W are held by the conventional end effector at the same time, the wafers W are once received by their respective wafer receiving portions R provided on blades B as illustrated in FIG. 21, and after that, the wafers W are pressed in one direction by a plunger (not illustrated) so as to be positioned (Patent Document 1).
Types of plungers include a type of pressing the wafers W by the plunger itself provided separately from the wafer receiving portions R, a type of pressing by the plunger the wafer receiving portions R on which their respective wafers W are placed, and the like. Anyway, in the conventional end effector, the plunger is necessary to position the wafers W.
However, using the plunger causes a problem such as the generation of particles, and even when the plunger cannot be used, it is required that the wafers can be positioned as if the plunger is used.
Also, as illustrated in FIG. 21, the height of the wafer receiving portion R is set to a substantially low height compared to the pitch between the blades B in the conventional end effector.
Note that, as the dimensions of the cassette C itself and a cassette placing table have actual article errors, the heights of the wafers W may be different between each cassette C. Therefore, the advancing height of the end effector has to be taught for each cassette C.
However, since the height of the wafer receiving portion R of the conventional end effector is relatively low as illustrated in FIG. 21, there is a problem that an allowable setting range in teaching the advancing height of the end effector is small and burden on the teaching operation is large.